Process for maximizing production of heavy naphtha from a hydrocarbon stream

ABSTRACT

Processes and apparatus for maximizing production of heavy naphtha from a hydrocarbon stream are provided. The process comprises providing a hydrocarbon feed stream comprising vacuum gas oil to a first hydrocracking reactor. The hydrocarbon feed stream is hydrocracked at first hydrocracking conditions comprising a first hydrocracking pressure to provide a first hydrocracked effluent stream therein. At least a portion of the first hydrocracked effluent stream is fractionated in a fractionation column to provide a heavy naphtha fraction. A kerosene stream is hydrocracked in a second hydrocracking reactor operating at second hydrocracking conditions comprising a second hydrocracking pressure to provide a second hydrocracked effluent stream. In an aspect, the first hydrocracking pressure can be greater than the second hydrocracking pressure by at least about 6895 kPa (g). At least a portion of the second hydrocracked effluent stream is passed to the fractionation column to maximize the production of heavy naphtha.

FIELD

The field particularly relates to a processes and apparatuses for maximizing production of heavy naphtha. More particularly, the technical field relates to hydrocracking of kerosene to maximize the production of heavy naphtha.

BACKGROUND

Currently, there is a growing demand for petrochemicals and refiners are striving to maximize the production of petrochemicals. With regulation in Asian countries such as India regarding use of LPG as a domestic fuel, demand for kerosene has decreased. Further, kerosene finds limited application as fuel or blend, and refining kerosene alone has economic constraints. Therefore, refiners are looking for alternate use of the distressed kerosene streams.

Heavy naphtha is primarily used as a petrochemical feedstock for running the aromatic complexes and naphtha crackers and produce more valuable petrochemical products. However, as heavy naphtha demand is increasing, refiners are looking for alternative processes to obtain heavy naphtha from less valuable hydrocarbons to produce more valuable products. Integrated refineries with petrochemical complexes are increasingly looking at value addition in terms of olefins and aromatic yields that are obtained from a barrel of crude oil.

Kerosene being a less valuable hydrocarbon, can be an alternate option to produce more valuable products. But, refiners are struggling to find an economical process for the conversion of distressed kerosene streams.

One of the widely use applications of kerosene is its use as a blending stream typically, with a diesel stream. However, kerosene use as a blending feedstock is limited and has economic constraints. An alternative method to convert kerosene into valuable products involves hydrocracking of kerosene. However, setting up a separate hydrocracking unit for kerosene increases capital expenditure. Further, the percentage conversion of kerosene and the products so obtained are not within the desired value/range e.g. lower retention of naphthenes and mono-aromatics.

Accordingly, it is desirable to provide new apparatuses and processes for converting the less valuable kerosene streams in to more valuable petrochemical feedstock. Further, there is a need for an alternative approach to maximize the conversion of kerosene to heavy naphtha with improved retention of naphthenes and mono-aromatics and which can be easily integrated with an existing hydroprocessing complex. Furthermore, other desirable features and characteristics of the present subject matter will become apparent from the subsequent detailed description of the subject matter and the appended claims, taken in conjunction with the accompanying drawing and this background of the subject matter.

BRIEF SUMMARY

Various embodiments contemplated herein relate to processes and apparatuses for upgrading a hydrocarbon feedstock. The exemplary embodiments taught herein provide a process for maximizing production of heavy naphtha from a hydrocarbon stream.

In accordance with an exemplary embodiment, a process is provided for maximizing production of heavy naphtha from a hydrocarbon stream comprises providing the hydrocarbon feed stream comprising vacuum gas oil to a first hydrocracking reactor. The hydrocarbon feed stream is hydrocracked in the presence of a hydrogen stream and a first hydrocracking catalyst in the first hydrocracking reactor at first hydrocracking conditions comprising a first hydrocracking pressure to provide a first hydrocracked effluent stream. At least a portion of the first hydrocracked effluent stream is fractionated in a fractionation column to provide a heavy naphtha fraction, a kerosene fraction, and a diesel fraction. A kerosene stream is hydrocracked in a second hydrocracking reactor operating at second hydrocracking conditions comprising a second hydrocracking pressure to provide a second hydrocracked effluent stream, the first hydrocracking pressure being greater than the second hydrocracking pressure by at least about 6895 kPa(g) (1000 psig). At least a portion of the second hydrocracked effluent stream is passed to the fractionation column to maximize the production of heavy naphtha.

In accordance with another exemplary embodiment, a process for maximizing production of heavy naphtha from a hydrocarbon stream comprises providing the hydrocarbon feed stream comprising vacuum gas oil to a first hydrocracking reactor. The hydrocarbon feed stream is hydrocracked in the presence of a hydrogen stream and a first hydrocracking catalyst in the first hydrocracking reactor operating at first hydrocracking conditions comprising a first hydrocracking pressure to provide a first hydrocracked effluent stream. At least a portion of the first hydrocracked effluent stream is passed to a first separator to provide a first vaporous stream and a first liquid stream. At least a portion of the first liquid stream is fractionated in a fractionation column to provide a heavy naphtha fraction, a kerosene fraction, and a diesel fraction. A kerosene stream is hydrocracked in a second hydrocracking reactor operating at second hydrocracking conditions comprising a second hydrocracking pressure to provide a second hydrocracked effluent stream, the first hydrocracking pressure being greater than the second hydrocracking pressure. The second hydrocracked effluent stream is passed to a second separator to provide a second vaporous stream and a second liquid stream. The entire second vaporous stream is passed to the second hydrocracking reactor. At least a portion of the second liquid stream is passed to the fractionation column to maximize the production of heavy naphtha.

In accordance with yet another exemplary embodiment, a process for maximizing production of heavy naphtha from a hydrocarbon stream comprises providing the hydrocarbon feed stream comprising vacuum gas oil to a first hydrocracking reactor. The hydrocarbon feed stream is hydrocracked in the presence of a hydrogen stream and a first hydrocracking catalyst in the first hydrocracking reactor operating at first hydrocracking conditions comprising a first hydrocracking pressure to provide a first hydrocracked effluent stream. At least a portion of the first hydrocracked effluent stream is fractioned in a fractionation column to provide a heavy naphtha fraction, a kerosene fraction, and a diesel fraction. A make-up hydrogen stream is compressed in at least two-stage compressor and a portion of a compressed make-up hydrogen gas stream is withdrawn upstream from a second compressor of the at least two-stage compressor. The remaining portion of the make-up hydrogen gas stream is compressed further in the at least two-stage compressor and passed to the first hydrocracking reactor as the hydrogen stream. A kerosene stream is hydrocracked in the presence of the portion of the compressed hydrogen gas to a second hydrocracking reactor operating at second hydrocracking conditions comprising a second hydrocracking pressure to provide a second hydrocracked effluent stream predominantly comprising naphtha, the first hydrocracking pressure being greater than the second hydrocracking pressure. At least a portion of the second hydrocracked effluent stream is passed to the fractionation column to maximize the production of heavy naphtha.

It is an advantage to have two separate hydrocracking reactors and operating the first hydrocracking reactor at pressure greater than at least about 7240 kPa(g) (1000 psig) compared to the second hydrocracking reactor with the second hydrocracking reactor operating at a low pressure of about 2758 kPa(g) (400 psig) bar to about 6550 kPa(g) (950 psig), to maximize the conversion of kerosene to heavy naphtha with improved retention of naphthenes and mono-aromatics. Further, the present flow scheme advantageously allows a second hydrocracker to be seamlessly integrated with an existing hydrocracker unit, by sharing its common asset infrastructure such as recycle gas compressor and make up hydrogen compressor.

These and other features, aspects, and advantages of the present invention will become better understood upon consideration of the following detailed description, drawing and appended claims.

BRIEF DESCRIPTION OF THE DRAWING

The various embodiments will hereinafter be described in conjunction with the following FIGURE.

The FIG. 1s a schematic diagram of a process and apparatus for maximizing production of heavy naphtha from a hydrocarbon stream in accordance with an exemplary embodiment.

Definitions

As used herein, the term “stream” can include various hydrocarbon molecules and other substances.

As used herein, the term “column” means a distillation column or columns for separating one or more components of different volatilities. Unless otherwise indicated, each column includes a condenser on an overhead of the column to condense the overhead vapor and reflux a portion of an overhead stream back to the top of the column. Also included is a reboiler at a bottom of the column to vaporize and send a portion of a bottom stream back to the bottom of the column to supply fractionation energy. Feeds to the columns may be preheated. The top pressure is the pressure of the overhead vapor at the outlet of the column. The bottom temperature is the liquid bottom outlet temperature. Overhead lines and bottom lines refer to the net lines from the column downstream of the reflux or reboil to the column. Alternatively, a stripping stream may be used for heat input at the bottom of the column.

As used herein, the term “overhead stream” can mean a stream withdrawn in a line extending from or near a top of a vessel, such as a column.

As used herein, the term “bottoms stream” can mean a stream withdrawn in a line extending from or near a bottom of a vessel, such as a column.

As used herein, the term “predominantly” can mean an amount of generally at least about 50% or at least about 75%, preferably about 85%, and optimally about 95%, by mole, of a compound or class of compounds in a stream.

As used herein, the term “rich” can mean an amount of generally at least about 50% or at least about 70%, preferably about 90%, and optimally about 95%, by mole, of a compound or class of compounds in a stream. Broadly, the term “rich” refers to the fact an outlet stream from a column has a greater percentage of a certain component that is present in the inlet feed to the column.

As used herein, the term “True Boiling Point” (TBP) means a test method for determining the boiling point of a material which corresponds to ASTM D2892 for the production of a liquefied gas, distillate fractions, and residuum of standardized quality on which analytical data can be obtained, and the determination of yields of the above fractions by both mass and volume from which a graph of temperature versus mass % distilled is produced using fifteen theoretical plates in a column with a 5:1 reflux ratio.

As used herein, the term “T5” or “T95” means the temperature at which 5 volume percent or 95 volume percent, as the case may be, respectively, of the sample boils using TBP or ASTM D-86.

As used herein, the term “heavy naphtha” means hydrocarbons boiling in the range using the True Boiling Point distillation method of T5 between about 20° C. (68° F.) and about 100° C. (212° F.), and T95 between about 140° C. (284° F.) and about 180° C. (356° F.).

As used herein, the term “kerosene” means hydrocarbons boiling in the range of between about 132° C. and about 300° C., using the True Boiling Point distillation method. Further, T5 boiling point for kerosene is from about 120° C. to about 200° C. and T95 boiling point is from about 250° C. to about 300° C.

As used herein, the term “separator” means a vessel which has an inlet and at least an overhead vapor outlet and a bottoms liquid outlet and may also have an aqueous stream outlet from a boot. A flash drum is a type of separator which may be in downstream communication with a separator. The separator may be operated at higher pressure.

As used herein, the term “passing” includes “feeding” and “charging” and means that the material passes from a conduit or vessel to an object.

As used herein, the term “N+2A” is taken as an index of reforming, wherein ‘N’ denotes percentage of naphthenes and ‘A’ denotes the percentage of mono-aromatics. “N+2A” is calculated as the volume percent of naphthenes in the naphtha plus 2 times the volume of mono-aromatics. A feed having a higher N+2A is a better-quality feed to produce high aromatics.

As used herein the term “substantially free” means a molar concentration less than 1.5 mole percent.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and is not intended to limit the various embodiments or the application and uses thereof. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description. The FIGURE have been simplified by the deletion of a large number of apparatuses customarily employed in a process of this nature, such as vessel internals, temperature and pressure controls systems, flow control valves, recycle pumps, etc. which are not specifically required to illustrate the performance of the invention. Furthermore, the illustration of the process of this invention in the embodiment of a specific drawing is not intended to limit the invention to specific embodiments set out herein.

As depicted, process flow lines in the FIGURE can be referred to, interchangeably, as, e.g., lines, pipes, branches, distributors, streams, effluents, feeds, products, portions, catalysts, withdrawals, recycles, suctions, discharges, and caustics.

An embodiment of a process for maximizing production of heavy naphtha from a hydrocarbon stream is addressed with reference to a process and apparatus 100 according to an embodiment as shown in the FIGURE. Referring to the FIGURE, the process and apparatus 100 comprises a hydrotreating reactor 120, a first hydrocracking reactor 130, a fractionation column 180, a second hydrocracking reactor 200, and a multistage compression system 300. As shown in the FIGURE, a hydrocarbon feed stream in line 102 comprising vacuum gas oil range components may be passed to a pre-heater 110 to pre-heat the hydrocarbon feed stream to obtain a pre-heated feed stream in line 112. Thereafter, the pre-heated feed stream in line 112 may be passed to a hydrotreating reactor 120. The pre-heater 110 may be optionally used to reduce the heat load on the downstream hydrotreating reactor. The pre-heated feed stream in line 112, may be combined with a compressed hydrogen stream in line 242 to obtain a combined stream in line 114 as described hereinafter in detail. The combined stream in line 114 may be passed to the hydrotreating reactor 120 for hydrotreating in the presence of a hydrotreating catalyst to provide a hydrotreated effluent stream in line 122. The compressed hydrogen stream may include recycled and/or make-up hydrogen, and as such may include other light hydrocarbon molecules, such as methane and ethane. Alternately, the hydrocarbon feed stream in line 102 may be combined with the compressed hydrogen stream and thereafter sent to the pre-heater 110. Typical hydrotreating conditions for the hydrotreating reactor 120 include a temperature from about 260° C. to about 426° C., a pressure from about 6895 kPa(g) (1000 psig) to about 21029 kPa(g) (3050 psig), and an LHSV of from about 0.1 hr⁻¹ to about 10 hr⁻¹. Suitable hydrotreating catalysts include a metal selected from the group consisting of nickel, cobalt, tungsten, molybdenum, and mixtures thereof, on a refractory inorganic oxide support.

In an alternate scheme, both the streams, the pre-heated hydrocarbon feed stream in line 112 and the hydrogen stream in line 242 may be sent to the hydrotreating reactor 120 separately. In accordance with an embodiment, the hydrocarbon feed stream in line 112 to the hydrotreating reactor 120 may comprise one or more of vacuum gas oil (VGO), light cycle oil (LCO), de-asphalted oil, and diesel.

The hydrotreating reactor 120 can include one or more beds of hydrotreating catalyst to provide the hydrotreated effluent stream in line 122. Although not shown in the FIGURE, the combined stream in line 114 may be separated into a plurality of streams. Therefore, a stream from the plurality of streams may be sent to a top hydrocracking catalyst bed and remaining streams being passed to the downstream hydrotreating catalyst beds in the hydrotreating reactor 120 as a quench stream for the stream coming through the upstream hydrotreating bed. Each bed can comprise similar or different catalyst compared to the other beds of the hydrotreating reactor. The hydrotreating reactor 120, provides for the removal of sulfur and/or nitrogen from the combined stream 114 to provide the hydrotreated effluent stream in line 122.

Subsequently, the hydrotreated effluent stream in line 122 may be passed to the first hydrocracking reactor 130. Accordingly, the hydrotreated effluent stream in line 122 is hydrocracked in the presence of a hydrogen stream and a first hydrocracking catalyst in the first hydrocracking reactor 130 at a first hydrocracking conditions comprising a first hydrocracking pressure to provide a first hydrocracked effluent stream in line 132. The first hydrocracking reactor 130 may include at least one or more beds of hydrocracking catalyst for hydrocracking the hydrotreated effluent stream to provide the first hydrocracked effluent stream in line 132. The first hydrocracking pressure can be from about 13790 kPa(g) (2000 psig) to about 17237 kPa(g) (2500 psig), or about 14479 kPa (2100 psig) to about 16547 kPa (g) (2400 psig).

The catalyst beds of first hydrocracking reactor 130 may comprise hydrocracking catalysts that utilize amorphous silica-alumina bases or low-level zeolite bases combined with one or more Group VIII or Group VIB metal hydrogenating components. The zeolite cracking bases are sometimes referred to in the art as molecular sieves and are usually composed of silica, alumina and one or more exchangeable cations such as sodium, magnesium, calcium, rare earth metals, etc. They are further characterized by crystal pores of relatively uniform diameter between about 4 and about 14 Angstroms. Zeolites having a relatively high silica/alumina mole ratio between about 3 and about 12 may be employed. Suitable zeolites found in nature include, for example, mordenite, stilbite, heulandite, ferrierite, dachiardite, chabazite, erionite and faujasite. Suitable synthetic zeolites include, for example, the B, X, Y and L crystal types, e.g., synthetic faujasite and mordenite. The preferred zeolites are those having crystal pore diameters between about 8-12 Angstroms, wherein the silica/alumina mole ratio is about 4 to 6. One example of a zeolite falling in the preferred group is synthetic Y molecular sieve.

The natural occurring zeolites are normally found in a sodium form, an alkaline earth metal form, or mixed forms. The synthetic zeolites are nearly always prepared first in the sodium form. In any case, for use as a cracking base it is preferred that most or all of the original zeolitic monovalent metals be ion-exchanged with a polyvalent metal and/or with an ammonium salt followed by heating to decompose the ammonium ions associated with the zeolite, leaving in their place hydrogen ions and/or exchange sites which have actually been decationized by further removal of water. Zeolites, such as Y zeolites may be steamed and acid washed to dealuminate the zeolite structure.

Mixed polyvalent metal-hydrogen zeolites may be prepared by ion-exchanging first with an ammonium salt, then partially back exchanging with a polyvalent metal salt and then calcining. In some cases, as in the case of synthetic mordenite, the hydrogen forms can be prepared by direct acid treatment of the alkali metal zeolites. In one aspect, the preferred cracking bases are those which are at least about 10 wt. %, and preferably at least about 20 wt. %, metal-cation-deficient, based on the initial ion-exchange capacity. In another aspect, a desirable and stable class of zeolites is one wherein at least about 20 wt. % of the ion exchange capacity is satisfied by hydrogen ions.

The active metals employed in the preferred hydrocracking catalysts of the present invention as hydrogenation components are those of Group VIII, i.e., iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum. In addition to these metals, other promoters may also be employed in conjunction therewith, including the metals of Group VIB, e.g., molybdenum and tungsten. The amount of hydrogenating metal in the catalyst can vary within wide ranges. Broadly speaking, any amount between about 0.05 percent and about 30 percent by weight may be used. In the case of the noble metals, it is normally preferred to use about 0.05 to about 2 wt %.

The foregoing catalysts may be employed in undiluted form, or the powdered catalyst may be mixed and copelleted with other relatively less active catalysts, diluents or binders such as alumina, silica gel, silica-alumina cogels, activated clays and the like in proportions ranging between about 5 and about 90 wt %. These diluents may be employed as such or they may contain a minor proportion of an added hydrogenating metal such as a Group VIB and/or Group VIII metal. Additional metal promoted hydrocracking catalysts may also be utilized in the process of the present invention which comprises, for example, aluminophosphate molecular sieves, crystalline chromosilicates and other crystalline silicates.

The hydrocracking catalyst preferably has high activity such as comprising at least about 40 to about 60 wt % dealuminated Y zeolite or at least about 15 to about 35 wt % non-dealuminated Y zeolite or at least about 3 to about 10 wt % beta zeolite, or some combination thereof yielding similar activity. In each case, mass-transfer limitations are expected to be significant and thus smaller-diameter extrudates such as 1/16 inch cylinders or 1/16 inch trilobes may give the best performance. The hydrocracking catalyst bed of the first hydrocracking reactor 130 may comprise about 30 to about 60% of the total catalyst volume in the first hydrocracking reactor 130.

Referring back to the FIGURE, at least a portion of the first hydrocracked effluent stream in line 132 is fractioned in a fractionation column to provide a heavy naphtha fraction, a kerosene fraction, and a diesel fraction. As shown, the first hydrocracked effluent stream in line 132 may be passed to a hot separator 140 to separate the first hydrocracked effluent stream into an overhead separator stream in line 142 and a bottoms separator stream in line 144. In an aspect, the hot separator 140 may be in direct communication with the first hydrocracking reactor 130 via the first hydrocracked effluent stream in line 132. Accordingly, the first hydrocracked effluent stream in line 132 may be passed directly to the hot separator 140. Suitable operating conditions of the hot separator 140 include, for example, a temperature of about 260 to 320° C.

The first vaporous stream in line 142 may be passed to a first cold separator 150 to provide a first vaporous stream in line 152 and a first liquid stream in line 154. Suitable operating conditions of the first cold separator 150 include, for example, a temperature of about 20 to 60° C. and just below the pressure of the second hydrocracking reactor 130. The first liquid stream in line 154 may be combined with the separator bottoms stream in line 144 from the hot separator 140 to provide a first combined liquid stream in line 156. The first combined liquid stream in line 156 may be sent to a common stripper 160 along with another liquid stream as described hereinafter in detail, for stripping. As shown, a second liquid stream in line 214 from a second cold separator 210 may be passed to the common stripper 160 along with the first combined liquid stream in line 156. Any suitable stripping media can be used in the common stripper 160 to separate the remaining gas fractions and to provide a stripped liquid stream in line 162. Preferably, the stripping media is steam. Accordingly, at least a portion of the first hydrocracked effluent stream and at least a portion of a second hydrocracked effluent stream are passed to the common stripper 160 before being passed to the fractionation column 180. The first vaporous stream in line 152 may be sent to a scrubber 230 to provide a hydrogen rich gaseous stream in line 232.

Thereafter, the stripped liquid stream in line 162 may be passed to a pre-heater 164 to heat the stripped liquid stream to a predetermined temperature before passing to the fractionation column 180 in line 166 to fractionate the stripped liquid stream into various fractions based on their boiling range including but not limited to a heavy naphtha fraction, a kerosene fraction, and a diesel fraction. In an aspect, stripped liquid stream in line 162 may be sent directly to the fractionation column 180. As shown, a naphtha fraction is withdrawn in line 182, a kerosene fraction is withdrawn in line 184, a diesel fraction is withdrawn in line 186, and an unconverted fraction is withdrawn in line 188.

In an exemplary embodiment as shown in the FIGURE, the kerosene fraction in line 184 may be passed to a side stripper 190 to provide a stripped kerosene fraction in line 192. A portion of stripped kerosene fraction in line 192 may be withdrawn in line 192A as a product stream. The remaining portion of stripped kerosene fraction in line 192 may be passed to the second hydrocracking reactor 200. As shown in the FIGURE, the stripped kerosene fraction in line 192 may be preheated prior to sending to the second hydrocracking reactor 200.

Moving now to the second hydrocracking reactor 200, a kerosene stream in line 196 is hydrocracked in the second hydrocracking reactor 200 operating at second hydrocracking conditions comprising a second hydrocracking pressure in the presence of hydrogen and second hydrocracking catalyst to provide a second hydrocracked effluent stream in line 202. In accordance with an exemplary embodiment as shown in the FIGURE, the kerosene stream in line 196 may comprise a combination of the kerosene fraction in line 192 and a kerosene fraction from an external source in line 194. In an alternate scheme, the kerosene stream in line 196 may comprise a kerosene fraction in line 194 from an external source only.

The second hydrocracking reactor 200 may comprise one or more beds of the second hydrocracking catalyst. Further, each bed may comprise similar or different catalyst compared to the other beds of the second hydrocracking reactor 200. The second hydrocracking catalyst of the second hydrocracking reactor can be similar or different compared the first hydrocracking catalyst of the first hydrocracking reactor 130 or can be a mixture thereof.

In an aspect, the second hydrocracking reactor 200 may operate at a second hydrocracking conditions comprising a second hydrocracking pressure, wherein the first hydrocracking pressure being greater than the second hydrocracking pressure by at least about 6895 kPa(g) (1000 psig). In alternative embodiments, the first hydrocracking pressure may be greater than the second hydrocracking pressure by greater than at least about 7240 kPa(g) (1050 psig), or at least about 7584 kPa(g) (1100 psig). Specifically, the second hydrocracking pressure may be from about 2758 kPa (g) (400 psig) bar to about 6550 kPa (g) (950 psig), or about 3999 kPa(g) (580 psig) to about 3999 kPa(g) (870 psig). Applicants have surprisingly found that operating the second hydrocracker pressure at this low pressure and particularly at a pressure of about 6895 kPa(g) (1000 psig) below that of the first hydrocracking pressure, still results in a satisfactory yield of naphtha.

The second hydrocracked effluent stream, withdrawn from the bottom of the second hydrocracking reactor 200 in line 202, may be passed to the fractionation column 180. As shown, the second hydrocracked effluent stream in line 202 may be passed to the second cold separator 210. The second cold separator 210 separates the second hydrocracked effluent stream to provide a second vaporous stream in line 212 and a second liquid stream in line 214. Suitable operating conditions of the cold separator 140 include, for example, a temperature of about 20 to 60° C. and just below the pressure of the second hydrocracking reactor 200.

At least a portion of the second liquid stream may be passed to the fractionation column 180. As shown in the FIGURE, the second liquid stream in line 214 may be passed to the common stripper 160 along with first combined liquid stream in line 156, or separately, and processed further as previously described. Accordingly, at least a portion of the first hydrocracked effluent stream and the at least a portion of the stripped second hydrocracked effluent stream are passed to the fractionation column 180.

Referring to second vaporous stream in line 212, as shown in the FIGURE, the entirety of the second vaporous stream may be passed to the second hydrocracking reactor 200. The second vaporous stream in line 212 comprises predominantly hydrogen and may be recycled to the second hydrocracking reactor 200 via a recycle line 222 after compressing to a predetermined pressure in a compressor 220. Applicants have discovered that the second vaporous stream is substantially free of impurities including hydrogen sulfide and ammonia. Accordingly, the entire of the vaporous stream which is further supplemented with a portion of the compressed make-up hydrogen stream in line 310A can be advantageously used in the second hydrocracking reactor. As shown, the recycle in line 222 may be combined with the kerosene stream in line 196 and then passed to the second hydrocracking reactor 200 in line 198. Although not shown in the FIGURE, the combined stream in line 198 may be preheated in a pre-heater and thereafter passed to the second hydrocracking reactor 200. In another aspect, the second vaporous stream in line 212 may be passed to the second hydrocracking reactor 200 separately.

Further, as shown in the FIGURE, a compression system 300 is provided to compress a make-up hydrogen stream in line 302. The compression system 300 may be a multistage compression system comprising at least two compressors. In an exemplary embodiment as shown in the FIGURE, the compression system 300 of the process of the present disclosure may comprise at least three compressors including a first compressor 310, a second compressor 320, and a third compressor 330. The compression system 300 may compress the make-up hydrogen stream in line 302 to provide compressed make-up hydrogen stream.

In an aspect, because the second hydrocracking reactor 200 operates at so much lower pressure than the first hydrocracking reactor 130, a portion of the compressed make-up hydrogen stream may be withdrawn upstream from a second compressor 320 of the compression system via line 310A. Accordingly, the portion of the compressed make-up hydrogen stream in line 310A is passed to the second hydrocracking reactor 200. The remaining portion of the make-up hydrogen stream may be further compressed in the second compressor 320 and the third compressor 330 and passed to the first hydrocracking reactor 130 as the compressed hydrogen stream in line 242. The compressed hydrogen stream in line 332 may be combined with the hydrogen rich gaseous stream in line 232 to provide the compressed hydrogen stream to the first hydrocracking reactor 130 via line 242.

Any of the above lines, conduits, units, devices, vessels, surrounding environments, zones or similar may be equipped with one or more monitoring components including sensors, measurement devices, data capture devices or data transmission devices. Signals, process or status measurements, and data from monitoring components may be used to monitor conditions in, around, and on process equipment. Signals, measurements, and/or data generated or recorded by monitoring components may be collected, processed, and/or transmitted through one or more networks or connections that may be private or public, general or specific, direct or indirect, wired or wireless, encrypted or not encrypted, and/or combination(s) thereof; the specification is not intended to be limiting in this respect. Further, the FIGURE shows one or more exemplary sensors such as 10 a, 10 b, 10 c, 10 d and 10 e located on or more conduits for sensing and transmitting data across a wired network or a cloud for controlling and/or and display purposes. Nevertheless, there may be sensors present on every stream so that the corresponding parameter(s) can be displayed and/or controlled accordingly.

Signals, measurements, and/or data generated or recorded by monitoring components may be transmitted to one or more computing devices or systems. Computing devices or systems may include at least one processor and memory storing computer-readable instructions that, when executed by the at least one processor, cause the one or more computing devices to perform a process that may include one or more steps. For example, the one or more computing devices may be configured to receive, from one or more monitoring component, data related to at least one piece of equipment associated with the process. The one or more computing devices or systems may be configured to analyze the data. Based on analyzing the data, the one or more computing devices or systems may be configured to determine one or more recommended adjustments to one or more parameters of one or more processes described herein. The one or more computing devices or systems may be configured to transmit encrypted or unencrypted data that includes the one or more recommended adjustments to the one or more parameters of the one or more processes described herein.

Applicants have found that using the proposed flow scheme enables maximizing the conversion of kerosene to heavy naphtha with improved retention of (N+2A). Specifically, applicants have found that operating the second hydrocracking reactor at a pressure of about 2758 kPa(g) (400 psig) to about 6550 kPa(g) (950 psig) and at pressure of at least below 6895 kPa(g) (1000 psig) than the first hydrocracking pressure results in improved retention of N+2A along with increased yield of heavy naphtha.

Example

Following is an example of the process for maximizing production of heavy naphtha from a hydrocarbon stream, in accordance with an exemplary embodiment of the process of the present disclosure as illustrated in the FIGURE. The example is provided for illustration purpose only and is not meant to limit the various embodiment of the process of the present disclosure in any way.

Several experiments were performed to check the effect of pressure on the conversion of kerosene to heavy naphtha. VGO was used as the feed and subjected to hydrocracking in a first hydrocracking reactor and second hydrocracking reactor.

In the exemplary run, VGO was subjected to hydrocracking in a first hydrocracking reactor operating at about 13790 kPa(g) (2000 psig) to provide a first hydrocracked effluent stream. The first hydrocracked effluent stream was then subjected to hydrocracking along with a kerosene stream in a second hydrocracking reactor operating at a second hydrocracking pressure lower than the first hydrocracking pressure. The second hydrocracking pressure was varied for the pressure study of the second hydrocracking reactor. The results so obtained are tabulated herein Table 1 below:

TABLE 1 At 75 wt % Conversion Pressure Differential Heavy Naphtha Yield Pressure (Second between the first from Second hydrocracking hydrocracking and second hydrocracking unit Heavy Naphtha reactor) hydrocracking reactor (wt. %) Quality (N + 2A) 9807 kPa (g) (1422 3983 kPa (g) (578 psig) 59 56 psig) 5884 kPa (g) (853 7906 kPa (g) (1147 psig) 59 61 psig) 3923 kPa (g) (569 9867 kPa (1431 psig) 59 64 psig) 2943 kPa (g) (427 10847 kPa (g) (1573 psig) 58 67 psig) 1961 kPa (g) (284 11829 kPa (g) (1716 psig) 55 72 psig)

As evident from Table 1, at 75 wt % conversion heavy naphtha yield is highest along with high N+2A when the second hydrocracking pressure is between about 5884 kPa(g) (853 psig) to about 2943 kPa(g) (427 psig). Applicants have found when the second hydrocracking pressure is about 9807 kPa(g) (1422 psig) i.e. when the second hydrocracking reactor is operating at a pressure difference of less than 6895 kPa(g) (1000 psig) as compared to the first hydrocracking reactor, N+2A of heavy naphtha decreases. Further, when the second hydrocracking pressure is about 1961 kPa(g) (284 psig); i.e. below 2758 kPa(g) (400 psig), heavy naphtha yield decreases to 55 wt %.

While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.

SPECIFIC EMBODIMENTS

While the following is described in conjunction with specific embodiments, it will be understood that this description is intended to illustrate and not limit the scope of the preceding description and the appended claims.

A first embodiment of the invention is a process for maximizing production of heavy naphtha from a hydrocarbon stream comprising providing the hydrocarbon feed stream comprising vacuum gas oil to a first hydrocracking reactor; hydrocracking the hydrocarbon feed stream in the presence of a hydrogen stream and a first hydrocracking catalyst in the first hydrocracking reactor at first hydrocracking conditions comprising a first hydrocracking pressure to provide a first hydrocracked effluent stream; fractionating at least a portion of the first hydrocracked effluent stream in a fractionation column to provide a heavy naphtha fraction, a kerosene fraction, and a diesel fraction; hydrocracking a kerosene stream in a second hydrocracking reactor operating at second hydrocracking conditions comprising a second hydrocracking pressure to provide a second hydrocracked effluent stream, the first hydrocracking pressure being greater than the second hydrocracking pressure by about 6895 kPa(g) (1000 psig); and passing at least a portion of the second hydrocracked effluent stream to the fractionation column to maximize the production of heavy naphtha. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the first hydrocracking pressure is greater than the second hydrocracking pressure by greater than about 7240 kPa(g) (1050 psig). An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the kerosene stream to the second hydrocracking reactor comprises a portion of the kerosene fraction from the fractionation column. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the kerosene stream to the second hydrocracking reactor comprises a kerosene fraction from an external source. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing the hydrocarbon feed stream through a hydrotreating reactor before being passed to the first hydrocracking reactor. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing at least a portion of the first hydrocracked effluent stream to a first separator to provide a first vaporous stream and a first liquid stream and passing at least a portion of the first liquid stream to the fractionation column. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising passing the second hydrocracked effluent stream to a second separator to provide a second vaporous stream and a second liquid stream and passing at least a portion of the second liquid stream to the fractionation column. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the at least a portion of the first hydrocracked effluent stream and the at least a portion of the stripped second hydrocracked effluent stream are passed to a common stripper before being passed to the fractionation column. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph further comprising compressing a make-up hydrogen stream in at least two-stage compressor and a portion of a compressed make-up hydrogen stream is withdrawn upstream from a second compressor of the at least two-stage compressor and passed to the second hydrocracking reactor. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein a remaining portion of the compressed make-up hydrogen stream is further compressed in the at least two-stage compressor and passed to the first hydrocracking reactor. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, further comprising at least one of sensing at least one parameter of the process for maximizing production of heavy naphtha and generating a signal or data from the sensing; generating and transmitting a signal; or generating and transmitting data.

A second embodiment of the invention is a process for maximizing production of heavy naphtha from a hydrocarbon stream comprising a) providing the hydrocarbon feed stream comprising vacuum gas oil to a first hydrocracking reactor; b) hydrocracking the hydrocarbon feed stream in the presence of a hydrogen stream and a first hydrocracking catalyst in the first hydrocracking reactor operating at first hydrocracking conditions comprising a first hydrocracking pressure to provide a first hydrocracked effluent stream; c) passing at least a portion of the first hydrocracked effluent stream to a first separator to provide a first vaporous stream and a first liquid stream; d) fractionating at least a portion of the first liquid stream in a fractionation column to provide a heavy naphtha fraction, a kerosene fraction, and a diesel fraction; e) hydrocracking a kerosene stream in a second hydrocracking reactor operating at second hydrocracking conditions comprising a second hydrocracking pressure to provide a second hydrocracked effluent stream, the first hydrocracking pressure being greater than the second hydrocracking pressure; f) passing the second hydrocracked effluent stream to a second separator to provide a second vaporous stream and a second liquid stream; g) passing the entire second vaporous stream to the second hydrocracking reactor; and h) passing at least a portion of the second liquid stream to the fractionation column to maximize the production of heavy naphtha. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, wherein the first hydrocracking pressure is from about 13790 kPa(g) (2000 psig) to about 17237 kPa(g) (2500 psig) and the second hydrocracking pressure is from about 2758 kPa(g) (400 psig) to about 6550 kPa(g) (950 psig). An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, wherein the first liquid stream and the second liquid stream are passed to a common stripper before being passed to the fractionation column. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, wherein the kerosene stream to the second hydrocracking reactor comprises a portion of the kerosene fraction from the fractionation column. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, wherein the kerosene stream to the second hydrocracking reactor comprises a kerosene fraction from an external source.

A third embodiment of the invention is a process for maximizing production of heavy naphtha from a hydrocarbon stream comprising a) providing the hydrocarbon feed stream comprising vacuum gas oil to a first hydrocracking reactor; b) hydrocracking the hydrocarbon feed stream in the presence of a hydrogen stream and a first hydrocracking catalyst in the first hydrocracking reactor operating at first hydrocracking conditions comprising a first hydrocracking pressure to provide a first hydrocracked effluent stream; c) fractionating at least a portion of the first hydrocracked effluent stream in a fractionation column to provide a heavy naphtha fraction, a kerosene fraction, and a diesel fraction; d) compressing a make-up hydrogen stream in at least two-stage compressor and a portion of a compressed make-up hydrogen gas stream is withdrawn upstream from a second compressor of the at least two-stage compressor; e) compressing the remaining portion of the make-up hydrogen gas stream further in the at least two-stage compressor and passed to the first hydrocracking reactor as the hydrogen stream; f) hydrocracking a kerosene stream in the presence of the portion of the compressed hydrogen gas to a second hydrocracking reactor operating at second hydrocracking conditions comprising a second hydrocracking pressure of to provide a second hydrocracked effluent stream predominantly comprising naphtha, the first hydrocracking pressure being greater than the second hydrocracking pressure; and g) passing at least a portion of the second hydrocracked effluent stream to the fractionation column to maximize the production of heavy naphtha. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph, wherein the first hydrocracking pressure is from about 13790 kPa(g) (2000 psig) to about 17237 kPa(g) (2500 psig) and the second hydrocracking pressure is from about 2758 kPa(g) (400 psig) to about 6550 kPa(g) (950 psig). An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph, wherein the kerosene stream to the second hydrocracking reactor comprises a portion of the kerosene fraction from the fractionation column. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the third embodiment in this paragraph, wherein the kerosene stream to the second hydrocracking reactor comprises a kerosene fraction from an external source.

Without further elaboration, it is believed that using the preceding description that one skilled in the art can utilize the present invention to its fullest extent and easily ascertain the essential characteristics of this invention, without departing from the spirit and scope thereof, to make various changes and modifications of the invention and to adapt it to various usages and conditions. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limiting the remainder of the disclosure in any way whatsoever, and that it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

In the foregoing, all temperatures are set forth in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated. 

1. A process for maximizing production of heavy naphtha from a hydrocarbon stream comprising: a) providing a hydrocarbon feed stream comprising vacuum gas oil to a first hydrocracking reactor; b) hydrocracking the hydrocarbon feed stream in the presence of a hydrogen stream and a first hydrocracking catalyst in the first hydrocracking reactor at first hydrocracking conditions comprising a first hydrocracking pressure to provide a first hydrocracked effluent stream; c) fractionating at least a portion of the first hydrocracked effluent stream in a fractionation column to provide a heavy naphtha fraction, a kerosene fraction, and a diesel fraction; d) hydrocracking a kerosene stream in a second hydrocracking reactor operating at second hydrocracking conditions comprising a second hydrocracking pressure to provide a second hydrocracked effluent stream, the first hydrocracking pressure being greater than the second hydrocracking pressure by at least about 6895 kPa(g) (1000 psig); and e) passing at least a portion of the second hydrocracked effluent stream to the fractionation column to maximize the production of heavy naphtha.
 2. The process of claim 1, wherein the first hydrocracking pressure is greater than the second hydrocracking pressure by at least about 7240 kPa(g) (1050 psig).
 3. The process of claim 1, wherein the kerosene stream to the second hydrocracking reactor comprises a portion of the kerosene fraction from the fractionation column.
 4. The process of claim 1, wherein the kerosene stream to the second hydrocracking reactor comprises a kerosene fraction from an external source.
 5. The process of claim 1 further comprising passing the hydrocarbon feed stream through a hydrotreating reactor before being passed to the first hydrocracking reactor.
 6. The process of claim 1 further comprising passing at least a portion of the first hydrocracked effluent stream to a first separator to provide a first vaporous stream and a first liquid stream and passing at least a portion of the first liquid stream to the fractionation column.
 7. The process of claim 1 further comprising passing the second hydrocracked effluent stream to a second separator to provide a second vaporous stream and a second liquid stream and passing at least a portion of the second liquid stream to the fractionation column.
 8. The process of claim 1, wherein the at least a portion of the first hydrocracked effluent stream and the at least a portion of the stripped second hydrocracked effluent stream are passed to a common stripper before being passed to the fractionation column.
 9. The process of claim 1 further comprising compressing a make-up hydrogen stream in at least two-stage compressor and a portion of a compressed make-up hydrogen stream is withdrawn upstream from a second compressor of the at least two-stage compressor and passed to the second hydrocracking reactor.
 10. The process of claim 9, wherein a remaining portion of the compressed make-up hydrogen stream is further compressed in the at least two-stage compressor and passed to the first hydrocracking reactor.
 11. The process of claim 1, further comprising at least one of: sensing at least one parameter of the process for maximizing production of heavy naphtha and generating a signal or data from the sensing; generating and transmitting a signal; or generating and transmitting data.
 12. A process for maximizing production of heavy naphtha from a hydrocarbon stream comprising: a) providing a hydrocarbon feed stream comprising vacuum gas oil to a first hydrocracking reactor; b) hydrocracking the hydrocarbon feed stream in the presence of a hydrogen stream and a first hydrocracking catalyst in the first hydrocracking reactor operating at first hydrocracking conditions comprising a first hydrocracking pressure to provide a first hydrocracked effluent stream; c) passing at least a portion of the first hydrocracked effluent stream to a first separator to provide a first vaporous stream and a first liquid stream; d) fractionating at least a portion of the first liquid stream in a fractionation column to provide a heavy naphtha fraction, a kerosene fraction, and a diesel fraction; e) hydrocracking a kerosene stream in a second hydrocracking reactor operating at second hydrocracking conditions comprising a second hydrocracking pressure to provide a second hydrocracked effluent stream, the first hydrocracking pressure being greater than the second hydrocracking pressure by at least about 6895 kPa(g) (1000 psig); f) passing the second hydrocracked effluent stream to a second separator to provide a second vaporous stream and a second liquid stream; g) passing the entire second vaporous stream to the second hydrocracking reactor; and h) passing at least a portion of the second liquid stream to the fractionation column to maximize the production of heavy naphtha.
 13. The process of claim 12, wherein the first hydrocracking pressure is from about 13790 kPa(g) (2000 psig) to about 17237 kPa(g) (2500 psig) and the second hydrocracking pressure is from about 2758 kPa(g) (400 psig) to about 6550 kPa(g) (950 psig).
 14. The process of claim 12, wherein the first liquid stream and the second liquid stream are passed to a common stripper before being passed to the fractionation column.
 15. The process of claim 12, wherein the kerosene stream to the second hydrocracking reactor comprises a portion of the kerosene fraction from the fractionation column.
 16. The process of claim 12, wherein the kerosene stream to the second hydrocracking reactor comprises a kerosene fraction from an external source.
 17. A process for maximizing production of heavy naphtha from a hydrocarbon stream comprising: a) providing a hydrocarbon feed stream comprising vacuum gas oil to a first hydrocracking reactor; b) hydrocracking the hydrocarbon feed stream in the presence of a hydrogen stream and a first hydrocracking catalyst in the first hydrocracking reactor operating at first hydrocracking conditions comprising a first hydrocracking pressure to provide a first hydrocracked effluent stream; c) fractionating at least a portion of the first hydrocracked effluent stream in a fractionation column to provide a heavy naphtha fraction, a kerosene fraction, and a diesel fraction; d) compressing a make-up hydrogen stream in at least two-stage compressor and a portion of a compressed make-up hydrogen gas stream is withdrawn upstream from a second compressor of the at least two-stage compressor; e) compressing the remaining portion of the make-up hydrogen gas stream further in the at least two-stage compressor and passed to the first hydrocracking reactor as the hydrogen stream; f) hydrocracking a kerosene stream in the presence of the portion of the compressed hydrogen gas to a second hydrocracking reactor operating at second hydrocracking conditions comprising a second hydrocracking pressure of to provide a second hydrocracked effluent stream predominantly comprising naphtha, the first hydrocracking pressure being greater than the second hydrocracking pressure by at least about 6895 kPa(g) (1000 psig); and g) passing at least a portion of the second hydrocracked effluent stream to the fractionation column to maximize the production of heavy naphtha.
 18. The process of claim 17, wherein the first hydrocracking pressure is from about 13790 kPa(g) (2000 psig) to about 17237 kPa(g) (2500 psig) and the second hydrocracking pressure is from about 2758 kPa(g) (400 psig) to about 6550 kPa(g) (950 psig).
 19. The process of claim 17, wherein the kerosene stream to the second hydrocracking reactor comprises a portion of the kerosene fraction from the fractionation column.
 20. The process of claim 17, wherein the kerosene stream to the second hydrocracking reactor comprises a kerosene fraction from an external source. 